Phosphonous acid esters phosphonite

Equation 28 represents the formation of oxoalkyl phosphonic acid esters (488 R = OR) or phosphinic esters (488 R = alkyl or aryl) from phosphite or phosphonite esters and appropriate halogen-containing ketones ( > 1) or acyl halides (n = 0), and supplements the formation of the phosphonoylated or phosphinoylated alkanoic acids through reactions 21 and 22 in the previous section. 

Two preparations of diesters of phosphonous acid have been reported, - One of these, which claims to be the first preparation of these derivatives, involves the reaction of ammonium hypophosphite with triaikylsilylamines to give bis(trialkylsilyl) esters (127) in excellent yield. These compounds are extremely reactive, e.g. they are spontaneously inflammable in air. Dialkyl phosphonites (128) have also been prepared by the reduction of... 

The hydrolysis of tervalent phosphorus acid derivatives with two P—C bonds leads to secondary phosphine oxides (50) and with one P—C bond to phosphonus acid derivatives (51). Chlorophosphines react rapidly with water, but aminophosphines, phosphinites and phosphonites often survive a short wash with aqueous NaHC03, an effective way to remove contaminating ammonium salts in the crude products. However, aminophosphines with small substituents, e.g. dimethylaminodimethylphosphine, aryl phosphinites and phosphonites and trimethylsilyl phosphinites and phosphonites are hydrolysed too quickly for such a treatment. The hydrolyses are catalysed by acids (the hydrolyses of phosphinites and phosphonites are also catalysed by OH ) and are much faster than hydrolyses of the corresponding phosphoryl compounds [up to a factor of 10 for acid-catalysed hydrolysis of (MeO)3P compared with (MeO)3P=0 ]. Dialkyl phosphonites are rapidly hydrolysed to the monoalkyl esters (51, X = OR) in weakly acidic water, whereas hydrolyses to phosphonous acids require reflux with strong acid or base, e.g. equation 131 Bis-(dialkylamino) phosphines may also be partially hydrolysed to phosphonous acid amides (51, X = NR2). Tervalent phosphorus acid derivatives with hydrogen sulphide give secondary phosphine sulphides or phosphonodithious acids, e.g. equation 156 . ... 

Reactions between haloketones and phosphonite esters, R P(OR)2, produce enol esters of phosphonic acids or esters of the phosphinic acids, R (R C0CH2)P(0)0R, depending on the halogen involved whilst phosphinite esters, R2POR yield the phosphinic acid esters R2P(0)0CPh=CHBr when treated with a,a-dibromoacetophenone . ... 

Replacement of one C-substituent in phosphines by an alkoxy or aryloxy group produces esters of phosphinous acid (phosphinites). Further substitution of alkyl or aryl by oxy groups gives first the diesters of phosphonous acid (phosphonites) and finally triesters of phosphorous acid (phosphites). Secondary phosphine oxides (SPOs) or heteroatom-substituted phosphine oxides (HASPOs), which are derived from the corresponding free acids by tautomerism, have been only occasionally investigated as ligands. However, they play a pivotal role as hydrolysis products of esters. In this role, they may exert an impact on the catalytic reaction. 

These reactions with phosphinites, phosphonites and phosphonates as well as phosphites have been utilized for the preparation of peptides and active esters of amino acids in good yields. 

In principle, the reaction between a dihaloalkane (9) and a phosphorus(III) ester (10 (R = alkyl, aryl or alkoxy) initially affords the haloalkyl compound 11 the use of a trialkyl phosphite would thus lead to an (co-haloalkyl)phosphonic diester 11 (R = alkoxy, R = alkyl), whilst that of a phosphonite diester (10 R = alkyl, aryl) would afford an (co-haloalkyl)alkyl(or aryl)phosphinic ester. Depending on the ratio of reactants, further reaction might then take place (pathway A), resulting in the formation of the compounds 12. Depending also on n, and on the reaction temperature, the alternative pathway B may be followed the products are then cyclic phosphonic or phosphinic acid derivatives 13, and examples following both reaction pathways have been discussed (chapter 2, Section A). 

As already mentioned, phosphonous esters, RP(OR )2, are extremely reactive to propenoic and 2-methylpropenoic acids, and the products have the structure 446 (R = H or Reactions have also been performed with silyl phosphonite esters (447 R =... 

Names of trivalent and pentavalent acids end in ous and ic , respectively. The overlap of organic and inorganic nomenclature should be noted. Esters of phosphonous and phosphinous acids are named phosphonites, HP (0R)2 and phosphinites H2P (OR), respectively. 

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